The present invention relates to a buckle.
Buckles have been used for a long time as tensioning and length adjusting devices, in particular in the aviation and road transport industries. For example, they have been used in conjunction with straps for securing a load or securing sheeting which is used to cover a load. Conventional buckles have a handle over which a strap is threaded, the handle being movable in an over centre manner to tension and secure the strap. Such buckles are generally known as over-centre buckles. The handle in an over-centre buckle is movable from an open position, in which a strap may be threaded onto the handle, to a closed position, in which the strap is secured under tension. The handles are generally provided with a locking mechanism for securing the handle in the closed position during use.
The present inventors have identified a problem with the conventional buckle design, namely that the buckle tends to allow the strap to slip when it is subjected to repetitive high frequency (e.g. 1 Hz), low force cyclic loads (e.g. gust loads experienced in aviation). This is thought to be due to the fact that when the tension is reduced the strap, which tends to be quite stiff, pushes through the buckle and loosens around the handle. When the tension is then reapplied this causes the strap to slip by a small amount. Through repeated cycles of loosening and tensioning the amount of strap slippage accumulates until the increase in strap length becomes quite noticeable and potentially dangerous.